Dynamic Phase Change Material for Heat Removal from Electronic Devices

Exemplary embodiments of the present disclosure relate to heat removal from electronic devices and, more particularly, to dynamic phase change material (PCM) for heat removal from electronic devices.

A characteristic property of phase change materials (PCMs) is that PCMs have a high latent heat of fusion. This allows PCMs to store a large amount of energy with a low temperature increase. As such, PCMs tend to be a solution to certain challenges in dynamic thermal management. A problem exists, however, in that another characteristic property of PCMs is that their energy density and power density tend to decrease as a transient melt front moves away from a heat source.

According to an aspect of the disclosure, a system is provided for heat transfer for an electronic device. The system includes a container, phase change material (PCM) at least partially filling the container in solid or liquid form, a screw disposed in the container and a drive element. The drive element is coupled with the screw and is configured to drive screw rotation to continuously and repetitively force the PCM in solid form through the container toward the electronic device whereupon electronic device heat liquifies proximal PCM and the PCM in liquid form along an exterior of the container away from the electronic device for PCM solidification.

In accordance with additional and/or alternative embodiments, the container is cylindrical.

In accordance with additional and/or alternative embodiments, the exterior of the container includes one or more grooves through which the PCM in liquid form is forced away from the electronic device.

In accordance with additional and/or alternative embodiments, the one or more grooves extend along a longitudinal axis of the container.

In accordance with additional and/or alternative embodiments, a heating element is disposed in the one or more grooves to maintain the PCM in liquid form.

In accordance with additional and/or alternative embodiments, a copper wire is disposed in thermal contact with the electronic device and in the one or more grooves to maintain the PCM in liquid form.

In accordance with additional and/or alternative embodiments, at least one of the screw is a single, monolithic member rotated by the drive element and the screw includes a non-rotating portion and a rotating portion which extends through the non-rotating portion and which is rotated by the drive element.

According to an aspect of the disclosure, a system is provided for heat transfer for an electronic device. The system includes an outer container, an inner container disposed within the outer container, phase change material (PCM) overfilling the inner container and at least partially filling the outer container in solid or liquid form, a screw disposed in the inner container and a drive element. The drive element is coupled with the screw and is configured to drive screw rotation to continuously and repetitively force the PCM in solid form through the inner container toward the electronic device whereupon electronic device heat liquifies proximal PCM and the PCM in liquid form between the inner and outer containers away from the electronic device for PCM solidification.

In accordance with additional and/or alternative embodiments, the outer container and the inner container are cylindrical.

In accordance with additional and/or alternative embodiments, the inner container includes one or more grooves on an exterior surface thereof through which the PCM in liquid form is forced away from the electronic device.

In accordance with additional and/or alternative embodiments, the one or more grooves extend along a longitudinal axis of the inner container.

In accordance with additional and/or alternative embodiments, a heating element disposed in the one or more grooves to maintain the PCM in liquid form.

In accordance with additional and/or alternative embodiments, a copper wire is disposed in thermal contact with the electronic device and in the one or more grooves to maintain the PCM in liquid form.

In accordance with additional and/or alternative embodiments, at least one of the screw is a single, monolithic member rotated by the drive element and the screw includes a non-rotating portion and a rotating portion which extends through the non-rotating portion and which is rotated by the drive element.

According to an aspect of the disclosure, a system is provided for heat transfer for an electronic device. The system includes an outer container, which is cylindrical, an inner container, which is cylindrical and disposed within the outer container to define an annular space between the inner and outer containers, phase change material (PCM) overfilling the inner container and at least partially filling the outer container in solid or liquid form, a screw disposed in the inner container and a drive element. The drive element is coupled with the screw and is configured to drive screw rotation to continuously and repetitively force the PCM in solid form through the inner container toward the electronic device whereupon electronic device heat liquifies proximal PCM and the PCM in liquid form through the annular space away from the electronic device for PCM solidification.

In accordance with additional and/or alternative embodiments, the inner container includes one or more grooves on an exterior surface thereof through which the PCM in liquid form is forced away from the electronic device.

In accordance with additional and/or alternative embodiments, the one or more grooves extend along a longitudinal axis of the inner container.

In accordance with additional and/or alternative embodiments, a heating element is disposed in the one or more grooves to maintain the PCM in liquid form.

In accordance with additional and/or alternative embodiments, a copper wire is disposed in thermal contact with the electronic device and in the one or more grooves to maintain the PCM in liquid form.

In accordance with additional and/or alternative embodiments, at least one of the screw is a single, monolithic member rotated by the drive element and the screw includes a non-rotating portion and a rotating portion which extends through the non-rotating portion and which is rotated by the drive element.

Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed technical concept. For a better understanding of the disclosure with the advantages and the features, refer to the description and to the drawings.

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.

As computing capabilities improve and applications call on electronics and microelectronics for increasingly complex and computationally expensive operations, a power draw and heat rejection in electronic devices can become rate-limiting. Furthermore, many products operate under size, weight and power (SWaP) constraints that can limit available mitigation strategies for cooling sub-system designs. Low SWaP cooling strategies that can scale down to microelectronic applications, but that are also applicable in macro-scale electronics, will tend to increase product capabilities.

PCMs offer improved cooling capacity performance for small-planform applications that historically relied on heat sinks (sensible heat capacity of sink) or heat fins (sensible heat capacity of sink and nearby air). PCMs provide cooling via the latent heat of phase transformation, which can have orders of magnitude higher specific capacity than sensible heat capacity. Although PCMs offer a higher cooling capacity, PCMs can also suffer from poor performance due to melt-pool growth that increases the distance between a heat source and solid PCM thereby increasing the thermal resistance and hindering cooling performance.

Existing strategies to mitigate thermal resistance growth from melt-pools include the addition of more thermally conductive materials like carbon or metal powders. These strategies tend to add weight and volume to the PCM thus limiting its specific cooling capacity. In some cases, the problem of the increased thermal resistance of the liquid layer of the PCM has been addressed by using a piston in a casing filled with PCM to exert a downward force on the PCM toward a heating element. As the heating element heats and melts the PCM, the downward force exerted by the piston drives the liquid PCM outwardly and urges the remaining solid PCM downwardly toward the heating element. While this action is useful in continuing to present solid PCM to the heating element, it is not continuous or repeatable since, at the end of the piston stroke, the system must be reset.

Thus, as will be described below, a system for dynamic PCM usage is provided for heat removal from electronic devices in order to continuously maintain a thin liquid PCM layer proximate to a heating element. The system continuously and repeatedly replaces liquid PCM with solid PCM and thereby maintains a thermal resistance of the liquid layer at a certain level.

In exemplary cases, a linear or a rotating configuration is provided with PCM filled pockets that are initially in solid phase. In each case, the PCM filled pockets move as they exchange heat with a heat source and the PCM in the PCM filled pockets melts and becomes liquified. As the PCM pockets move, a solid pack of PCM comes in contact with the heat source and the old pack of PCM, which is now liquified, will solidify through a cooling process (i.e., through convection or cold plates) to be ready for the next turn. The moving can be powered by an electrical actuator such as a stepper motor or a PCB motor. In other exemplary cases, a spiral actuator or a dual spiral actuator replaces liquid PCM with solid PCM as the spiral actuator or the dual spiral actuator rotates. The rotation can be provided actively by a stepper type motor or passively using a shape-memory-alloy spring. The spring may be torsional or may use an axial-to-rotational movement mechanism. In yet another exemplary case, a screw is turned down to push melted and liquified PCM outwardly and away from a heat source. The liquid PCM passes through grooved sides of a container reaches the top of the container where it returns to the bottom, driven by the screw. A copper (or any thermally conductive) wire can be inserted in the grooved sides to prevent the solidification of the liquified PCM in the grooved sides by conducting heat from the heat source to the PCM. This ensures that the PCM is still in the liquid phase once it reaches the top of the container and solidifies while the screw is turned down.

1 1 FIGS.A andB 101 102 101 110 111 120 102 130 120 121 122 110 123 121 110 112 111 111 120 124 110 With reference to, a systemis provided for heat transfer for an electronic device. The systemincludes packsthat are filled with PCM, an annular bodythat is partially adjacent to the electronic deviceand a drive element. The annular bodyhas a rotational axisand includes a surfaceon which the packsare disposed in an annular arrangementabout the rotational axis. Each of the packscan have a circular segment shapeand may, in some cases, include a membrane in which the PCMis stored, where the membrane is non-porous with respect to the PCM. The annular bodycan include insulating separation wallsthat are annularly interleaved between neighboring ones of the packs.

130 120 120 121 120 110 102 111 110 130 120 121 121 The drive elementis coupled with the annular bodyand is configured to drive a rotational movement of the annular bodyin forward or reverse rotational directions about the rotational axis. This rotational movement of the annular bodysequentially brings one or more of the packsinto and then out of heat transfer proximity with the electronic devicefor a heat transfer duration that is sufficient to melt at least a portion or all of the PCMof the one or more of the packsin a continuous and repetitive manner. The drive elementcan include or be provided as at least one or more of a stepper motor and a printed circuit board (PCB) motor. In either case, the rotational movement of the annular bodycan be one of discrete (i.e., the rotational movement rotates about the rotational axisby a predetermined angular value, stops and restarts repeatedly) and continuous (i.e., the rotational movement rotates continuously about the rotational axis).

110 102 110 102 110 111 110 102 111 110 111 110 111 110 140 111 While the one or more of the packsare sequentially brought into and then out of heat transfer proximity with the electronic device, other ones of the packsare remote from the electronic device. Within these remote ones of the packs, the portion or all of the PCMthat has been melted cools and solidifies, thus making the remote ones of the packsready for their next exposure to the electronic device. The cooling and solidification of the PCMof the remote ones of the packscan be one of passive cooling and active cooling. In the passive cooling, the PCMof the remote ones of the packsradiates heat outwardly and/or conducts heat to ambient air/atmosphere. In the active cooling, the PCMof the remote ones of the packsradiates heat outwardly and/or conducts heat to ambient air/atmosphere and a coolantcan be provided to actively remove heat from the PCM.

120 110 102 111 110 The continuous and repetitive manner of the above-mentioned sequence is provided such that the rotational movement of the annular bodycan continue indefinitely without pause or a need for a system reset with the one or more of the packsbeing brought into and then out of the heat transfer proximity with the electronic devicefor the heat transfer duration that is sufficient to melt the at least the portion or all of the PCMof the one or more of the packs.

102 110 102 111 110 120 110 As used herein, the heat transfer proximity can be defined as a distance from the electronic deviceto the one or more of the packsat which heat of the electronic deviceis transferred to and sufficient to melt the at least the portion or all of the PCMof the one or more of the packsduring the time of the heat transfer duration. As used herein, the heat transfer duration can be a function of the speed of the rotational movement, the dimensions of the annular bodyand the dimensions of the packs.

110 In accordance with embodiments, only a single one of the packsmay be brought into and then out of the heat transfer proximity for the heat transfer duration at a time.

2 2 FIGS.A andB 201 202 201 210 211 220 202 230 220 221 222 210 223 221 210 212 211 211 220 224 210 With reference to, a systemis provided for heat transfer for an electronic device. The systemincludes packsthat are filled with PCM, a linear bodythat is partially adjacent to the electronic deviceand a drive element. The linear bodyhas a longitudinal axisand includes a surfaceon which the packsare disposed in a linear arrangementalong the longitudinal axis. Each of the packscan have an elongate shapeand may, in some cases, include a membrane in which the PCMis stored, where the membrane is non-porous with respect to the PCM. The linear bodycan includes insulating separation wallsthat are linearly interleaved between neighboring ones of the packs.

230 220 120 221 220 110 202 211 210 230 220 221 221 The drive elementis coupled with the linear bodyand is configured to drive a linear movement of the linear bodyin forward or reverse rotational directions along the longitudinal axis. This linear movement of the linear bodysequentially brings one or more of the packsinto and then out of heat transfer proximity with the electronic devicefor a heat transfer duration that is sufficient to melt at least a portion or all of the PCMof the one or more of the packsin a continuous and repetitive manner. The drive elementcan include or be provided as at least one or more of a stepper motor and a printed circuit board (PCB) motor. In either case, the linear movement of the linear bodycan be one of discrete (i.e., the linear movement moves along the longitudinal axisby a predetermined distance, stops and restarts repeatedly) and continuous (i.e., the linear movement moves continuously along the longitudinal axis).

210 202 210 202 210 211 210 202 211 210 211 210 211 210 240 211 While the one or more of the packsare sequentially brought into and then out of heat transfer proximity with the electronic device, other ones of the packsare remote from the electronic device. Within these remote ones of the packs, the portion or all of the PCMthat has been melted cools and solidifies, thus making the remote ones of the packsready for their next exposure to the electronic device. The cooling and solidification of the PCMof the remote ones of the packscan be one of passive cooling and active cooling. In the passive cooling, the PCMof the remote ones of the packsradiates heat outwardly and/or conducts heat to ambient air/atmosphere. In the active cooling, the PCMof the remote ones of the packsradiates heat outwardly and/or conducts heat to ambient air/atmosphere and a coolantcan be provided to actively remove heat from the PCM.

220 210 202 211 210 The continuous and repetitive manner of the above-mentioned sequence is provided such that the linear movement of the linear bodycan continue indefinitely without pause or a need for a system reset with the one or more of the packsbeing brought into and then out of the heat transfer proximity with the electronic devicefor the heat transfer duration that is sufficient to melt the PCMof the one or more of the packs.

202 210 202 211 210 220 210 As used herein, the heat transfer proximity can be defined as a distance from the electronic deviceto the one or more of the packsat which heat of the electronic deviceis transferred to and sufficient to melt the at least the portion or all of the PCMof the one or more of the packsduring the time of the heat transfer duration. As used herein, the heat transfer duration can be a function of the speed of the linear movement, the dimensions of the linear bodyand the dimensions of the packs.

210 In accordance with embodiments, only a single one of the packsmay be brought into and then out of the heat transfer proximity for the heat transfer duration at a time.

3 3 FIGS.A andB 4 6 FIGS.- 301 302 301 310 302 311 310 320 310 311 330 310 312 302 313 320 312 310 330 320 320 311 311 311 311 320 311 311 302 302 311 311 311 302 311 1 2 1 2 With reference toand to, a systemis provided for heat transfer for an electronic device. The systemincludes a containerthat is partially adjacent to the electronic device, PCMat least partially filling the containerin solid form or liquid form, a spiral actuatorthat is disposed in the containerwith the PCMand a drive element. The containercan be block-shaped and can include a lower surfacethat is adjacent to the electronic deviceand sidewalls. In these or other cases, the spiral actuatorcan be arranged proximate to the lower surfacein a center of the container. The drive elementis coupled with the spiral actuatorand is configured to drive rotation of the spiral actuatorto continuously and repetitively force corresponding movements of the portionof the PCMthat is in solid form and the portionof the PCMthat is in liquid form. That is, the rotation of the spiral actuatorcontinuously and repetitively forces the portionof the PCMthat is in solid form toward the electronic devicewhereupon heat of the electronic deviceliquifies proximal PCMand, at the same time, continuously and repetitively forces the portionof the PCMthat is in liquid form away from the electronic devicefor solidification of the PCM.

3 3 FIGS.A andB 320 320 320 321 322 323 324 325 323 324 325 321 323 324 320 330 321 324 325 324 311 311 312 302 323 325 323 311 311 313 313 311 1 1 1 1 2 In accordance with embodiments and, as shown in, the spiral actuatorcan include or be provided as a single-phase spiral actuator. The single-phase spiral actuatorhas a rotation axisand a single, unitary finwith a leading edge, a trailing edgeand a bodythat is disposed between the leading edgeand the trailing edge. The bodyforms a ramp curvature about the rotation axisfrom the leading edgeto the trailing edge. In these or other cases, as the single-phase spiral actuatoris rotated by the drive elementabout the rotation axis, the trailing edgeand the portion of the bodyproximate to the trailing edgeforce the portionof the PCMthat is in solid form downwardly toward the lower surfaceand the electronic devicewhile the leading edgeand the portion of the bodythat is proximate to the leading edgeforce the portionof the PCMthat is in liquid form outwardly toward the sidewallsand upwardly along the sidewallsfor PCMsolidification.

4 FIG. 3 3 FIGS.A andB 3 3 FIGS.A andB 3 3 FIGS.A andB 320 320 301 320 326 327 328 327 328 322 320 330 326 327 311 311 312 302 328 311 311 313 313 311 320 329 327 328 2 2 2 1 2 2 In accordance with embodiments and, as shown in, the spiral actuatorcan include or be provided as a dual-phase spiral actuatorfor use in the systemof. The dual-phase spiral actuatorhas a rotation axis, a first finand a second fin. The first finand the second finare configured similarly as the single, unitary finofbut with opposing ramp curvature pitches. In these or other cases, as the dual-phase spiral actuatoris rotated by the drive element(see) about the rotation axis, the first finwould force the portionof the PCMthat is in solid form downwardly toward the lower surfaceand the electronic devicewhile the second finwould force the portionof the PCMthat is in liquid form outwardly toward the sidewallsand upwardly along the sidewallsfor PCMsolidification. The dual-phase spiral actuatorcan further include a partitionto separate the opposing ramp curvature pitches of the first finand the second fin.

5 FIG. 3 3 FIGS.A andB 3 3 FIGS.A andB 320 320 341 342 301 341 342 320 343 322 341 342 320 330 343 341 311 311 312 302 342 311 311 313 313 311 320 344 341 342 3 3 3 1 2 3 In accordance with embodiments and, as shown in, the spiral actuatorcan include or be provided as a dual-phase spiral actuatorwith multiple opposing spiral screws (i.e., first spiral screwand second spiral screw) for use in the systemof. The first and second spiral screwsandof the dual-phase spiral actuatorhave a common rotation axisand are each configured similarly as the single, unitary finofbut with opposing screw configurations. In these or other cases, as the first and second spiral screwsandof the dual-phase spiral actuatorare each rotated by the drive elementabout the common rotation axis, the first spiral screwwould force the portionof the PCMthat is in solid form downwardly toward the lower surfaceand the electronic devicewhile the second spiral screwwould force the portionof the PCMthat is in liquid form outwardly toward the sidewallsand upwardly along the sidewallsfor PCMsolidification. The dual-phase spiral actuatorcan further include a partitionto separate the opposing screw configurations of the first spiral screwand the second spiral screw.

330 601 320 6 FIG. The drive elementcan include or be provided as at least one or more of a stepper motor and a printed circuit board (PCB) motor and/or a shape-memory alloy spring where the shape-memory alloy spring is a torsional spring and the shape-memory alloy spring includes an axial-to-rotational movement mechanism(see). In any case, the rotation of the spiral actuatorcan be one of discrete (i.e., the rotation rotates by a predetermined angular value, stops and restarts repeatedly) and continuous (i.e., the rotation rotates continuously).

7 11 FIGS.- 701 702 701 710 720 710 725 7201 720 7101 710 710 720 With reference to, a systemis provided for heat transfer for an electronic device. The systemincludes an outer container, which can be but is not required to be cylindrical, and an inner container, which can be but is not required to be cylindrical, and which is disposed within the outer containerto define an annular spacebetween an exterior surfaceof the inner containerand an interior surfaceof the outer container. For purposes of clarity and brevity, the outer containerand the inner containerwill be described as cylindrical and coaxial, but it is to be understood that this is not required and that other configurations and arrangements are possible.

710 711 702 712 711 720 721 702 722 721 720 710 721 720 711 710 721 720 722 720 712 710 722 720 The outer containerhas a first endthat can be disposed proximate to the electronic deviceand a second endopposite the first endand the inner containerhas a first endthat can be disposed proximate to the electronic deviceand a second endopposite the first end. The inner containeris shorter than the outer containersuch that the first endof the inner containeris slightly higher than the first endof the outer containerto allow for flow of liquified PCM beneath the first endof the inner containerand such that the second endof the inner containeris lower than the second endof the outer containerto allow for overflow of the liquified PCM over the second endof the inner container.

701 730 720 722 720 710 740 720 750 750 740 740 731 730 731 730 740 731 730 720 702 702 730 731 730 725 702 730 1 2 1 2 The systemfurther includes PCMthat overfills the inner containerabove the second endof the inner containerand that at least partially fills the outer containerin solid or liquid form, an auger or screw (hereinafter referred to as a “screw”)that is disposed in the inner containerand a drive element. The drive elementis coupled with the screwand is configured to drive rotation of the screwto continuously and repetitively force corresponding movements of the portionof the PCMthat is in solid form and the portionof the PCMthat is in liquid form. That is, the rotation of the screwcontinuously and repetitively forces the portionof the PCMthat is in solid form downwardly through the inner containerand toward the electronic devicewhereupon heat of the electronic deviceliquifies proximal PCMand, at the same time, continuously and repetitively forces the portionof the PCMthat is in liquid form upwardly through the annular spaceand away from the electronic devicefor solidification of the PCM.

8 8 FIGS.A andB 9 FIG. 7201 720 801 731 730 702 801 7202 720 701 901 801 901 702 801 901 731 730 730 722 720 720 901 801 2 2 As shown in, the exterior surfaceof the inner containercan include one or more groovesthrough which the portionof the PCMthat is in liquid form can flow while being forced away from the electronic device. In accordance with embodiments, the one or more groovescan extend along a longitudinal axisof the inner container. As shown in, the systemcan further include a heating element, such as a copper wire, which is disposed in the one or more groovesto maintain the PCM in liquid form. The heating elementcan be heated by being disposed in thermal contact with the electronic deviceand/or can be heated by an external heat source. In any case, the one or more grooveswith or without the heating elementare configured to maintain a liquified state of the portionof the PCMthat is in liquid form at least until the PCMis able to flow over the second endof the inner containerand into an interior of the inner container. The presence of the heating elementin the one or more groovesaids in this liquid state maintenance.

10 FIG. 11 FIG. 740 1001 750 740 1101 1102 1101 750 1101 As shown in, the screwcan include or be provided as a single, monolithic memberthat is rotated as one single monolithic element by the drive element. As shown in, the screwcan include or be provided as a non-rotating portionand a rotating portionthat extends through the non-rotating portionand that is rotated by the drive elementwhile the non-rotating portionis static.

Technical effects and benefits of the present disclosure are the provision of systems and methods for dynamic PCM usage for heat removal from electronic devices. The systems and methods effectively add to the reliability of the electronic devices as the phase change process of the PCM dampens sudden temperature spikes.

The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” can include a range of ±8% or 5%, or 2% of a given value.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.

While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.